1. Field of the Invention
The present invention relates to a variable attenuator applied to a modulator design at microwave and millimeter-wave frequency bands. For maintaining the quality of microwave RF signal processing, the variable attenuator is designed for achieving the wide attenuation range and low phase-shifting over all attenuation range.
2. Description of the Prior Art
The prior art variable attenuator cannot achieve a wide attenuation range and low phase-shifting over all attenuation range.